Sexual Differentiation

Question 1

Gonadal Ridge

Answer 1

Thickened area on the ventromedial surface of the mesonephros

Question 2

PGCs

Answer 2

Migrate to the gonadal ridge via the dorsal mesentary of the hindgut and are rapidly surrounded by cords of somatic cells

*Sex chromosomes of the somatic cells dictate the differentiation of the gonad

Question 3

First discernible event of testis differentiation

Answer 3

Presence of Sertoli cells; aggregate around PGCs to form the testis cords

Question 4

Appearance of Leydig cells

Answer 4

Week 8-9; appear in b/w the developing seminiferous tubules

Question 5

Primitive Sex cords

Answer 5

Extend deep into the medulla of the developing gonads and make contact w/ the epithelium that eventually becomes the tunica albuginea

=>Secondary cords and seminiferous tubules later develop (hardened until puberty)

*Sertoli cells promote this by secreting paracrine factors as well as Leydig proliferation, peritubular myloid cells, and endothelial cells for male vasculature

Question 6

Requirements for Ovary differentiation (3)

Answer 6

1. Invasion of the cortex (not medulla) by PGCs
2. Reactivation of the inactivated X-chromosome
3. Absence of a Y-chromosome

Question 7

Ovarian Genesis

Answer 7

Large pool of oogonia is formed at Week 11 and some leave the pool and enter meiosis until Prophase I

Question 8

Primordial follicles

Answer 8

Formed at Week 13 when granulosa cells aggregate around the oocyte and are covered by a basal lamina

• By Week 20, oogonial mitosis begins to decline and development of follicles decreases
• Infant will have all the primordial follicles it will ever have by 6 months old

Question 9

Male Genital Tract Differentiation

Answer 9

Degradation of the Mullerian ducts from Week 7-10 (mediated by AMH)
-released by Sertoli cells

AND

Proliferation of the Wolffian ducts (mediated by testosterone)
=>Vas deferens, epididymis, seminal vesical, prostate

Question 10

Female Genital Tract Differentiation

Answer 10

Persistence of the Mullerian Ducts

AND

Degradation of the Wolffian Ducts

*Occurs in the lack of hormone stimulation

Question 11

Syndrome of persistent Mullerian Ducts

Answer 11

Normal phenotypic male does not produce AMH and has poorly developed female internal genitalia

*Often present in an inguinal hernia

Question 12

Male External Genitalia Differentiation

Answer 12

Occurs w/ the presence of dihydrotestosterone formed from the action of 5a-reductase

*Female external genitalia forms in absence of this

Question 13

Differentiation of the urogenital sinus

Answer 13

Males => Prostatic Buds

Females => Inferior walls of the vagina

Question 14

Syndrome of Complete Androgen Resistance

Answer 14

Male and female internal genitalia is absent; external genitalia is female

-AMH still being secreted means loss of Mullerian; no testosterone means loss of Wolffian

Question 15

5a-reductase deficiency

Answer 15

Internal genitalia will be male; external will be ambiguous

*External may develop more @ puberty

Question 16

SRY Deficiency

Answer 16

Will be a phenotypic female due to lack of SOX 9 and Sertoli cell production

Question 17

47 XXY

Answer 17

Klinefelter’s Syndrome: Pts. will be tall (no closure of epiphyseal plates) and have hypogonadism w/ hyalinized tubules

Symptoms include: Gynecomastia
Tall
High-pitched voice
Increased GnRH, FSH, and LH
Increased E2

Question 18

SOX9

Answer 18

Encoded by the SRY gene on the Y chromosome; regulates the expression of products that promote Sertoli cell differentiation

Question 19

Genital tubercle

Answer 19

Becomes the glans penis or clitoris

Question 20

Genital swelling

Answer 20

Becomes the scrotum or the labia majora

Question 21

Genital folds

Answer 21

Become the ventral penile folds or the labia minora

Question 22

Barr bodies

Answer 22

Inactive X chromosome; males should have none

-Genes in pseudo autosomal region escape inactivation

Question 23

Cortical cords

Answer 23

Second wave of cord formation in an XX embryo that eventually break into distinct clusters that are..

=>primordial follicle

Question 24

INSL-3

Answer 24

Promotes testicular descent along w/ testosterone

-Also made in the Leydig cells

Question 25

Loss of Intracellular bridges

Answer 25

Occurs when spermatozoa are released into the lumen of the seminiferous tubule